The US superstar himself famously came back from a three-year lay-off, with a detached retina, to beat countryman Marvin Hagler in 1987.

“There are parallels here because, when I suffered my detached retina, people were totally against me coming back as they thought I could go blind,” he said.

This will be Brook's comeback from a fractured eye socket (Image: Action Images via Reuters)

“My doctor, my ophthalmologist said, ‘Ray, if you want to go back, your eye is strong enough that you’ll be OK.’ I didn’t go into that ring thinking about my eye. If I had, I could not have pulled off what I did.

“I imply the same thing with Kell. I’m sure his doctor and ophthalmologist have said, ‘You’re OK.’”

Leonard – part of boxing folklore due to his clashes with Hagler, Roberto Duran and Thomas Hearns – insists it could be a close fight after initially favouring his fellow American.

“When the fight was announced, I definitely slightly leaned towards Errol Spence,” he said. “It’s more intriguing than I’d assumed. It will be based upon who has the best preparation and sticks to the game plan.”